1. Field of the Invention
Embodiments of the invention relate to a touch sensing device and a double sampling method thereof.
2. Discussion of the Related Art
User interface (UI) is configured so that users are able to communicate with various electronic devices and thus can easily and comfortably control the electronic devices as they desire. Examples of the user interface include a keypad, a keyboard, a mouse, an on-screen display (OSD), and a remote controller having an infrared communication function or a radio frequency (RF) communication function. User interface technologies have continuously expanded to increase user's sensibility and handling convenience. The user interface has been recently developed to include touch UI, voice recognition UI, 3D UI, etc.
The touch UI has been used in portable information appliances and has been expanded to the use of home appliances. There is a mutual capacitive touch screen as an example of a touch screen for implementing the touch UI. The mutual capacitive touch screen can sense proximity input as well as touch input and also recognize respective multi-touch (or multi-proximity) inputs.
A method for sensing the touch screen input includes sensing an output voltage to a touch sensor and comparing a voltage change amount before and after a touch input with a predetermined threshold voltage or counting the change in voltage. Other methods have been known. As a method for reducing an influence of noise added in the touch sensor of the mutual capacitive touch screen, there is a method for removing DC offset included in a received voltage of the touch sensor using a digital-to-analog converter (DAC). In the mutual capacitive touch screen, the noise includes high frequency noise, DC offset, and interference between Tx or Rx channels, etc. The noise reduces a signal-to-noise ratio (often abbreviated SNR) of a signal read from the touch sensor and thus reduces the sensitivity of the touch sensor. If a ground of a touch object, for example, a finger is shaken, the noise is generated along a Tx line passing through a touch point. Because the number and the amount of noise increase as the number of multi-touch inputs increases, it is difficult to distinguish the touch points from one another.